Preparation And Properties Of Modified Chitosan Coating Materials Of Fertilizers

Chitosan is an amino polysaccharide, which possess unique properties, such as film forming ability, antibacterial, biocompatibility and biodegradability. Chitosan has been widely applied in medicine, food and environmental protection. However, there was a little with respect to the report of chitosan as a slow-release fertilizer coating materials. As the coating material of slow-release fertilizer, chitosan can reduce the release rate of nutrient. It also has antibacterial properties and degradability in the soil. Chitosan is harmless to the environment. It is an excellent slow-release fertilizer coating material.Unmodified chitosan film is easy to swell, which greatly limits its application in slow-release fertilizer. In this paper, three kinds of chitosan slow-release fertilizer coating materials were prepared by chemical modifications. This paper mainly discussed the structure factors’ effect on release performance of chitosan coated slow-release fertilizers, including hydrophobic/hydrophilic character, thermal stability, crystallinity, urea permeability.(1) Chitosan was modified by crosslinking agent with glyoxal and glutaraldehyde. The results indicated that the crystallinity was decreased and hydrophobicity was increased by crosslinking agent. Thermal change weight demonstrated that crosslinking agent enhanced thermal properties. With the increasing content of crosslinking agent, the accumulated permeation amount of urea dropped, and chitosan crosslinked with glutaraldehyde dropped rapidly.(2) Acylated chitosan with different length of carbon chain was synthesized. Different substituted acylated chitosan slow-release fertilizer coating materials were prepared. The effect of structure on the properties of membrane was studied. Experimental results show that with the increase of substitution, the hydrophobic enhanced, the crystallinity and thermal stability decreased. The accumulated permeation amount of urea decreased, and chitosan acylated with caprylyl chloride decreased rapidly. When acylated chitosan degree of substitution is 0.07, the accumulated permeation amount of urea is minimum.(3) Acylated chitosan was modified by crosslinking with glutaraldehyde. The results indicated that the crystallinity was decreased and hydrophobicity was increased by crosslinking. Thermal change weight demonstrated that crosslinking enhanced thermal properties. With the increasing content of glutaraldehyde, the accumulated permeation amount of urea dropped rapidly from 74.7% to 34.2% in seven days. The accumulated permeation amount of urea was 76.7% on the 28th, this indicated that the crosslinked and acylated chitosan films had an excellent controlled-release property.